In WCDMA (Wideband Code Division Multiple Access) networks based on 3GPP (Third Generation Partnership Project) rel-7 and earlier, one user equipment (UE) receives and transmits data on one carrier frequency only.
Due to non-orthogonality between users, resulting in interference leakage between them, the system throughput for uplink is limited to 2-3 Mbps in scenarios with multiple users. 3GPP has specified support for uplink user rates of 6-12 Mbps in a system. This means that the aim 1s to have user experience of high throughput at low load.
Multicarrier WCDMA has been proposed in 3GPP, meaning simultaneous transmission to/from one UE on many carriers (3GPP TR-25.814). The aim 1s to achieve optimal load balancing over many carriers.
Support of a time division multiplexing (TDM) scheduling mode in uplink has also been proposed in 3GPP TR-25.823.
A network operator can classify a user as High Data Rate (HDR) user or Low Data Rate (LDR) user, according to its data rate need. Based on this, 3GPP rel-7 does not prevent the introduction of interference cancellation (IC) in uplink for HDR users to reduce interference for LDR users. The aim 1s however to experience high throughput also with multiple HDR users. This requires IC also between HDR users, which is costly.
An alternative solution is to introduce TDM scheduling on uplink, meaning that IC only has to be performed on one HDR user at a time. To be efficient TDM scheduling should only be used when the scheduled user can fully utilize allocated TDM resources. The fraction of the traffic not able to fully utilize allocated TDM resources should therefore remain in code division multiplexing (CDM) mode. Dynamic switching between CDM mode and TDM mode may be done based on knowledge of buffer status in the UE. This mixture of TDM and CDM modes within a carrier may also be applied to the multicarrier concept, thus one user can transmit data on many carriers simultaneously, using either CDM or TDM mode on each carrier. L1 signalling may be used by the network to send individual access grants in order to control the allowed uplink rate for each user and carrier.
In the existing solution, LDR traffic in CDM mode is mixed with HDR users in TDM mode, on which IC is applied. The stability of this solution is questionable due to the following:                High variation of IC efficiency on TDM scheduled HDR users.        High data rate variation between TDM scheduled HDR users.        High absolute power variation on TDM scheduled HDR users due to power control.        
This creates an unstable and fluctuating radio environment for LDR users in CDM scheduled mode. This may result in higher required Signal-Interference Ratio (SIR) for the LDR traffic, meaning lower capacity. Maintaining the Quality of Service (QoS) for LDR users, also for LDR users with high SIR, will be more difficult. In order to keep these fast radio fluctuations under control, the rate of the HDR users have to be set conservatively and thereby eliminating the goal of high data rates by means of TDM scheduling in combination with IC.
Furthermore even if IC is applied within a cell it can not reduce the inter-cell interference, which will further limit possibility for higher data rates in the system. More advanced IC techniques can be used to deal with this, but it can only reduce interference from very few users in neighbour cells.
A problem addressed by the invention is thus to overcome or at least mitigate at least one of the above-indicated difficulties.